1. Technical Field
This disclosure relates to the removal of specimens inside energetic-beam instruments, such as focused ion beam (FIB) microscopes and the preparation of specimens for later analysis in the transmission electron microscope (TEM) and elsewhere, and apparatus to facilitate these activities.
2. Background
The use of in situ lift-out (INLO) for TEM sample preparation in the dual-beam FIB has become a popular and accepted technique. The INLO technique is a series of FIB milling and sample-translation steps used to produce a site-specific specimen for later observation in a TEM or other analytical instrument. Removal of the lift-out sample is typically performed using an internal nanomanipulator in conjunction with the ion-beam assisted chemical-vapor deposition (CVD) process available with the FIB tool. A suitable nanomanipulator system is the Omniprobe AutoProbe 300, manufactured by Omniprobe, Inc., of Dallas, Tex. Details on INLO methods may be found in the specifications of U.S. Pat. Nos. 6,420,722 and 6,570,170. These patent specifications are incorporated into this application by reference, but are not admitted to be prior art with respect to the present application by their mention in the background.
Gas chemistries play an important role in INLO. Gas injection in the FIB may be used for etching to speed the milling process, for ion or electron-beam assisted CVD of oxides, metals and other materials, for deposition of protective layers, and for deposition of planarizing material, such as silicon dioxide, to fill holes where lift-out samples have been excised. For a number of reasons, gas injection systems mounted on the wall of the FIB vacuum chamber have become preferred. This offers a safety advantage over injection systems using gas sources or bottled gases that are external to the FIB vacuum chamber. Chamber-mounted injection systems also permit whole-wafer analysis and can be easily inserted to place a gas nozzle near (within 50 μm) the position where the charged particle beam strikes the sample. After completion of the injection process, the system can be retracted to a safe position for normal FIB sample translation operations. An example of a gas injection system is disclosed in US Patent Publication No. 2009/0223451. This patent specification is incorporated into this application by reference, but is not admitted to be prior art with respect to the present application by its mention in the background.
There are a growing number of gas chemistries of interest and researchers typically require more than one chemistry on the same instrument. This is commonly achieved by installing additional gas injection systems that use up additional ports on the instrument. Each gas injection system has to be customized to suit the instrument and port and reagent being used. For example, there may be an “inappropriate” port on a certain instrument that, although unoccupied and thus available for mounting a gas injection system, would orient a gas injection system at an angle that would adversely affect the gas injection system's performance (e.g. allowing flow of a liquid source into the delivery path, resulting in release of a liquid undesirably into the instrument vacuum chamber). Thus there are a limited number of appropriate ports on a typical FIB, and a growing number of desired accessories that may need to be installed on these ports. Therefore, providing additional gas chemistries will not only be costly, but can also compromise the flexibility for a researcher to use other accessory instrumentation. A solution is required that can be easily adapted for use on a variety of energetic beam instruments and which offers the researcher a safe and efficient way to use more than one gas chemistry without compromising the other uses of the microscope.